Audio-equipment maker Monster LLC and its chief executive sued Apple Inc.’s Beats Electronics LLC, its co-founders Jimmy Iovine and Dr. Dre, and Taiwanese smartphone maker HTC Corp. for allegedly conspiring to dupe Monster out of a deal with Beats before the company was sold to Apple for $3.2 billion last year.

In a complaint filed in Superior Court in San Mateo County, Calif., Monster said Beats “fraudulently acquired” the Beats by...